By the time we pass under the third sign depicting a man getting a leg blown off by a landmine, Lucy is shooting me daggers. In five years of travelling together, my girlfriend and I have always struggled to get it right. Her concept of the perfect break – relaxation, a good book, the occasional indulgence – just isn't that compatible with my travelling ethos, which is the sort that gets you into adventures or, more often, lost.

A beach holiday in West Africa had seemed the perfect compromise. By taking advantage of cheap charter flights to Gambia, we could explore a small wedge of the coast on a budget – plenty of beachside inertia for her, the prospect of less-explored territory for me. So we had spent the first two days on the spacious beaches of Kartong in the far south of Gambia, most of it idled away under a palm-frond sunshade with the ocean to ourselves. For Lucy this had been bang on the money. I had been slightly bored.

And now I had persuaded her to cross the border at Séléti, and into the crucible of Africa's most enduring conflict. Since 1982, the region that sits immediately below Gambia, Basse Casamance, has been gripped by what the analysts describe as a "low-level uprising" precipitated by separatists seeking independence from the rest of Senegal. The FCO warns against travel to many parts of the region, but we were following the less anxious rule-of-thumb propounded elsewhere: that travel here is safe enough provided you keep abreast of the latest news, steer clear of the unruly bits and stick to the main roads in daylight hours.

We knew that, in recent years, this fertile region has enjoyed a fragile calm and that among southern Europeans our destination, the coastal resort of Cap Skirring (or "Cap" as it is known for convenience), has been a quietly popular source of winter sun for decades. At least, this is what I keep reminding Lucy, and myself, as the brackish creek water and tangled mangroves of the Casamance interior flash past the car window.

"It has been very quiet for the last year," says taxi driver Buba reassuringly, before promptly undermining this statement with an anecdote of how, five years ago, he was shot at by bandits not far from here after running a blockade. Behind me, Lucy gives a despairing sigh.

Her chagrin does not last for long, however. Soon after arriving in Cap, we stumble onto a scene to make all fear subside: a deep crescent bay, backed by stands of palm trees; the sand is so fine that it squeaks underfoot and the foreshore is laced with receding arcs of foam. Lucy concedes that coming here may have been a good idea after all.

As we explore the surrounding area it's evident that, somewhat perversely, tourism in Cap has benefited from the surrounding region's endemic instability, which has stymied the influx of visitors and checked the kind of hasty overdevelopment that has scarred Gambia's tightly packaged coast. Here the constructions are more sympathetic, with budget encampments sitting cheek-by-jowl with unobtrusive luxury resorts, all perched on an embankment overlooking the beach. Even the huge Club Med compound manages to remain fairly inoffensive, while away from the soulless main drag of tourist restaurants and djembe bars, the labyrinthine town retains a local heartbeat.

We stay at Le FaLaFu, a Swiss-run joint located off a sandy lane half a mile south of town. The buildings encircle a courtyard garden that is vivid with flowers and the territorial chivvies of swifts and flycatchers, criss-crossed with pathways made of cockle shells. There are few other guests here and we get the pick of the lodgings: an airy room with traditional pastel drawings hung on aquamarine walls and a huge whitewashed balcony out back with views of the beach unfurling to the north and south.

For the next few days I'm content to do things Lucy-style: jumping the waves in the warm and playful ocean, bargaining with the beach hawkers over sand paintings and kola-nut necklaces, and napping on the balcony to the soporific sound of the crashing surf below. After two days, to placate what restlessness remains, we rent a couple of antiquated mountain bikes and find that it is possible to cycle north along the beach all the way to Nyikine village, where there are views across the mouth of the Casamance river to the old slave-trading post of Karabane island.

That evening we go for dinner at Buvette, the first in a row of restaurants de la plage that sit next to the ranks of dry-docked pirogues immediately north of Club Med. The setting is romantic in the way that only a tumbledown place can be – the awning constructed from reclaimed flotsam and bits of boat, its stanchions decorated with ragged bunches of bougainvillea. We place our order and a young boy named Élage is dispatched down the beach. After 10 minutes he returns with a plastic bucket containing the main ingredient of our meal – two sea bass, subsequently grilled and served in a spectacular yassa, a zingy Casamancais speciality of lime and onions. We eat by the light of a single candle in a plastic bottle with our toes in the sand as the sun dissolves into the horizon.

Inexplicably, by the next day this sort of relaxation has become too much and I find myself pining to move on. To the north, Casamance boasts other, more laid-back, resorts in Abéné and Kafountine, but I come up with what I think is a better idea – to head south into country number three. Half an hour later, I come back from the internet café waving a printout of Portuguese vocabulary and present my sunbathing paramour with the guidebook, open at the section for Guinea-Bissau. She thumbs the pages for 10 minutes with much muttering and rolling of eyes.

The exasperation is perhaps understandable. Guinea-Bissau is one of the poorest countries in the world, better known as an entrepot for narco-traffickers smuggling contraband to Europe than for its astonishing coastline. For added frisson the country's erstwhile leader, President João Vieira – the self-proclaimed "God's gift to Guinea-Bissau" – had been assassinated a month before. The main export is cashew nuts. Lucy is allergic to them.

An unlikely winter bronzing destination then, but I can tell Lucy is secretly quite sold on this coastal escapade and the following dawn finds us taking the first bush taxi inland to Ziguinchor, the provincial capital of Basse Casamance, where we pop into the sleepy Guinea-Bissau consulate for visas.

"You must be going to Fatima's," says the amiable official, handing back our freshly stamped passports. I nod bemused, oblivious to what he might have meant until day's end when we trundle into the scattering of adobe huts that comprise the Guinea-Bissau village of Varela.

Fatima, it transpires, is the vivacious, local-born proprietor of Varela's sole hotel, and is therefore the reason why anyone but the most grizzled pioneer can holiday here at all. Named after Fatima's mother, Chez Helene is one of those secret places that I write about with some reluctance, lest the revelation somehow lead to its demise. In a corner of the world where plumbed-in water is more luxury than expectation, residents of Fatima's clean and simple rooms are blessed with generator-driven electricity (Guinea-Bissau has no energy grid), hammocks strung across patches of shade, a fine chef in the shape of Fatima's Italian husband Franco and, what seems most critical of all after 50 miles of bouncing down the rutted laterite road that is the only means to get here, refrigerated beer.

There's nothing to do in Varela but that really is the point. Apart from a flurry of local enterprise and market barter down on the Praia de Pescadores, the region's endless coastline is deserted, space enough for thousands to find some littoral solitude, let alone the two dozen French and Portuguese tourists currently ensconced at Chez Helene.

We see out the days sitting above the beach, towels draped on a low escarpment of oxidised earth that changes with the movement of the sun, from ochre to orange to russet-brown. At dusk, when the earth flames reddest, the men wade across the mudflats to go circle-netting in the shallows, and children come to giggle at us from behind the trees. It's close to paradise. Lucy is converted to the ethos of adventure.

The only surprise is that, with Gambia's Identikit resorts less than one degree of latitude to the north, there are no other Britons here to share it. "It's still a word of mouth place, Varela," Fatima muses later, as the first strands of merengue pump out of the bar to call her guests to their dinner of fresh langoustine. "I don't think the British even know we are here."

GETTING THERE

Thomas Cook Airlines (0844 412 5970; www.thomascook.com) operates charter flights from Gatwick, Birmingham and Manchester to the Gambian capital Banjul from £237 return between November 2009 and April 2010.

STAYING THERE

A night in a basic roundhouse at the Boboi Beach Lodge (00220 777 6736; www.gambia-adventure.com), just north of Kartong, costs £16.